A method of making metallic rings for use in gas turbine engines is disclosed in a Japanese patent application Sho 62-2889. The method discloses, in part:
1. Cold rolling of a nickel or cobalt based metallic ring body with the use of a plurality of rolls. PA1 2. Initial forming steps are aimed primarily to elongate the ring body in the axial direction. PA1 3. The subsequent forming steps are needed to increase the ring diameter with the use of several pairs of rolls. PA1 4. As illustrated conceptually in FIGS. 4 and 5, the disclosed method is designed to perform roll forming while enclosing the cross section of the work piece completely within the forming rolls. PA1 1. Achievement of tight limits on manufacturing tolerances within .+-.0.002 inches without having to resort to later machining and hot rolling steps; and PA1 2. Efficient shaping in the axial direction of the cross sectional shape is achieved early in the forming process in the initial hot working phase of fabrication. PA1 (a) to produce severe shape changes on an inner or outer ring surface cost effectively; PA1 (b) to reduce the quantity of forming rolls required significantly to about three pairs so as to produce savings in the manufacturing and handling costs for the forming rolls; and PA1 (c) to improve the quality of the ring body. PA1 (a) preparing a metallic stock material of a ring-shape (henceforth referred to as the stock material), having an inner diameter which is not larger than an inner diameter of a completed ring body, and whose cross sectional area in the axial direction is not less than a cross sectional area of the completed ring body; PA1 (b) placing the stock material between a pair of rolls consisting of a shaping roll and a forming roll; PA1 (c) forming a locally thinned ring-shaped depressed region (RSDR) depressed in the radial direction with the shaping roll on a peripheral surface of the stock material; PA1 (d) performing roll forming of the stock material while maintaining a separation between the shaping roll and the forming roll; PA1 (e) applying a radial compressive force to the RSDR so as to increase the axial dimension of the stock material. PA1 (1) continue to roll form until the dimension of one of the inner diameter, outer diameter or the axial dimension reaches a predetermined value; PA1 (2) machine to final dimensions after the completion of roll forming the stock material; PA1 (3) roll form the surface shapes on the peripheral surface with the shaping roll while controlling the deformation at the peripheral surface in contact with the forming roll; PA1 (4) divide the ring body at a plane perpendicular to the axis after the completion of roll forming of the stock material; PA1 (5) form the initial RSDR in the central axial region of the stock material; PA1 (6) form the surface shapes so as to be symmetrical about a plane perpendicular to the axis; PA1 (7) form the initial RSDR while restraining the transfer of mass of the stock material in the axial direction; PA1 (8) control the drifting of the stock material in the axial direction by engaging a protrusion section of the shaping roll with the initial RSDR on the stock material. PA1 (9) after the completion of an intermediate fabrication stage, roll form shapes while permitting the surface being formed to move freely in the axial direction; PA1 (10) form shapes on a peripheral surface of the stock material while restraining the drifting of the stock material by firmly holding the stock material between the surface being formed and the corresponding shaping roll; PA1 (11) form a tapered surface on the stock material such that the diameter toward the axial end is larger than the diameter at the central region of the ring body on a peripheral surface of the stock material; PA1 (12) form a tapered surface on the stock material such that the diameter toward the axial end is smaller than the diameter at the central region of the ring body on a peripheral surface of the stock material; PA1 (13) perform compression roll forming by cold rolling; PA1 (14) after the completion of the intermediate fabrication stage, a shaping roll is shared between the intermediate and final fabrication stages; PA1 (15) form the ring body using materials suitable for use in gas turbine engines; PA1 (16) perform intermediate annealing in between the roll forming operations; PA1 (17) form a shape change region in the vicinity of the axial ends of the stock material; PA1 (18) form a shape change region in the vicinity of the initial RSDR; PA1 (19) inspect the dimension of the diameter of the ring body stock, which refer to in-process ring bodies intermediate between the stock material and the completed ring body, during the final forming stages. PA1 1. According to the present invention of fabricating surface shapes on a peripheral surface of the stock material, the following advantages accrue. PA1 2. Further, PA1 3. Further, PA1 4. Further, by parting the formed ring body at a plane perpendicular to the axial of the ring body into two portions, it is possible to obtain two ring bodies readily, thereby enabling to increase the manufacturing productivity. PA1 5. Further, by forming the initial RSDR in the central axial region of the stock material, it is possible: PA1 6. Further, because the stock material is symmetric in the axial direction, it is possible: PA1 7. Further, by forming the initial RSDR on the stock material while restraining the axial shift of the stock material, it becomes possible to correctly position and accurately form the initial RSDR in the specified position in the axial direction of the stock material, thereby permitting the subsequent forming steps to be carried out with precision, using the RSDR as the reference base. PA1 8. Further, PA1 9. Further, PA1 10. Further, by restraining the axial shift of the stock material by contacting the shaped surface of the stock material with a respective shaping roll, it is possible to provide precision shapes in the correct regions of the ring body. PA1 11. Further, PA1 12. Further, PA1 13. Further, by conducting the roll forming operation by cold rolling, it is possible to minimize microstructural transformations of the metallic material, thereby enabling to achieve improved uniformity of the ring body. PA1 14. Further, by sharing one common roll in roll forming after the intermediate fabrication stage, it becomes possible to decrease the quantity of shaping rolls required for forming a shaped surface. PA1 15. Further, PA1 16. Further, by providing intermediate annealing steps, hardening which may take place due to cold rolling can be controlled, thereby improving the subsequent formability. PA1 17. Further, it is possible to improve the formability of the stock material by enlarging the RSDR, thereby facilitating the material flow in the axial end direction thereof. PA1 18. Further, because a mass transfer of the stock material occurs to the axial ends of the RSDR during the formation of the RSDR on the stock material, the formability of the stock material in the vicinity of the RSDR is improved. PA1 19. Further, by controlling the forming process by means of diameter checking of the ring body stock, the generation of excess material regions is controlled, thereby improving the operational efficiency of the final fabrication stage.
The features of such a method are said to be:
However, when such a method is examined closely for application to, for example, AMS5754 alloy (SAE, Society for Automotive Engineers, alloy designation) for making metallic rings of the required tight tolerances for gas turbine engines, it is realized that such a process requires over seventeen pairs of forming rolls, with the attendant problems of high cost of manufacturing the rolls, high effort expended in changing the rolls, lengthening of cold roll processing and high cost of manufacturing small lots of different shapes. Therefore, improvements in such aspects of manufacturing are needed before the above method becomes industrially useful.